In the sensing technique of a conventional handwriting system (e.g., a virtual handwriting pad), the sensed objects may not be recognized correctly due to the background light source interference resulted from the varying of operational environments. In other words, the conventional handwriting system may have a performance easily affected by the background light.
In addition, because the operational environment (e.g., a table's top surface) may vary, the predetermined operation zone (i.e., a virtual input zone) of the conventional handwriting system may not be always convenient for users. For example, users may feel inconvenient to operate the conventional handwriting system if the table's top surface (specifically, the predetermined operation zone) associated with the handwriting system is disorder.